1. Field of the Invention
This invention relates to a manual method and apparatus for applying a flexible adhesive strip around the perimeter edge of a rigid substrate. More particularly, the present invention relates to an improved manual method and apparatus for applying an insulating edge strip onto glass sheets as part of the manufacturing process of insulating glass units.
2. Description of the Prior Art
Insulating glass units can be manufactured using a horizontal or vertical production line.
The advantages of vertical unit production include: higher productivity; lower equipment costs; less floor space; convenient glass handling, including; large glass sheets, easy on-line gas filling, and simpler automation of various unit production operations, including, glass feed, glass movement, unit assembly and sealant gunning.
To simplify the production of insulating glass units, various adhesive strip products have been developed. One such product is described in U.S. Pat. 4,831,799. The product is manufactured from flexible thermoset rubber foam that incorporates desiccant fill material and features a vapor barrier backing film and acrylic side adhesive. The side adhesive is protected by a flexible release liner that allows the material to be packaged on reels. This adhesive strip product has been commercialized by Edgetech IG Inc and is marketed under the registered trademark of Super Spacer(copyright).
Adhesive strip products are typically applied with the glass in a horizontal position. As described in U.S. Pat. No. 5,246,331 issued to Hallahan et al, an air flotation assembly table is typically used. To reduce worker movement to a minimum, the air flotation table features a moveable suction cup that successively rotates the glass through 90xc2x0 and linearly moves the glass to a convenient position close to the perimeter edge of the table. Although the glass is located close to the operator, the hand tool must be held in position as the glass is rotated around. As a result, there can be abnormal movement of the operator""s body including: prolonged spinal curvature; unnatural trunk rotation, and hyperextension of the shoulder, elbow and arm. In the long term, this abnormal movement may potentially cause repetitive stress disorders and related health problems.
For manual application of adhesive strip products on a vertical production line, the glass sheets are tilted down to a horizontal position for strip application and the strip is applied using conventional rotating tables and hand tools. For unit assembly, the glass sheets must then be tilted back into a vertical position and because of this extra glass movement, productivity is reduced.
The adhesive strip product described in U.S. Pat. No. 4,831,799 incorporates a vapor barrier backing. To provide corner continuity of the vapor barrier, a half circular notch is made in the spacer and this creates a flex point that allows for easy corner formation. Various application tools have been developed for forming these notched corners and as documented in photographs of a prototype Edgetech application tool, one way of forming these corner notches is through the use of a slidable circular punch. When activated, the hollow punch removes a half circular portion or slug of strip material. Because of the acrylic side adhesive, these slugs adhere together and as a result, the slug material can be easily ejected from the tool. The advantage is that the tool can remain in continuous contact with the glass and the productivity of strip application is improved.
At the final corner, there are further productivity advantages if the tool can also incorporate a blade for cutting through the adhesive strip. As described in U.S. Pat. No. 5,472,558 issued to Lafond, one approach is add a separate blade that operates in combination with the punch to both notch and cut through the adhesive strip at the final corner.
Although productivity is improved, experience has shown that this simultaneous operation of the punch and cutting blade requires a complicated punch design that is expensive to manufacture and is prone to wear and damage.
Compared to the earlier Edgetech tools, another new feature of the Lafond tool is that both the pneumatic cylinder and strip feeding channel are steeply inclined at angle and this has the advantage of a reduced channel length between the pneumatic cylinder and the pressure wheel. However, the drawback is that after strip cut-off, the tool requires to be re-threaded and this can be a time consuming operation.
For operating the pneumatic cylinder, the Lafond tool also features a finger trigger that is located below a cylindrical handle and operated by means of a finger pulling action. With horizontal strip application using a rotary table, there are three main ergonomic drawbacks to this arrangement. First, it provides for wrist deviation with rapid finger movement. Second, it combines forceful gripping with a twisting action and third, it requires rapid and forceful pronation with strong elbow and wrist flexion.
The tool of U.S. Pat. No. 5,472,558 Lafond is also limited to producing a notched corner. An alternative corner application detail is to partially cut through the back face of the adhesive strip and create an open-ended corner. Although in this arrangement the barrier film is not continuous, the open-ended corner allows for additional sealant material to be applied at the corners and this ensures that the edge-seal integrity of the insulating glass unit is not downgraded.
The present invention provides a hand tool for applying adhesive strip material to a substrate having an edge and a major face, said hand tool comprising: a body having a lower surface and a channel extending therethrough adjacent said lower surface for receiving a strip of material therein; a substrate positioning member located close to said channel on said lower surface of said body for guiding said tool along said edge of said substrate, said lower surface of said body being elevated from said major face by said strip when said strip is fed through said channel; an adjustable wheel for applying pressure on said strip to urge said strip to adhere with said substrate major face; and a cutting mechanism mounted on said body, said cutting mechanism being selectively operable for partially cutting said strip and for fully cutting said strip.
The cutting mechanism is preferably provided by a cutter and a displacement means that is selectively operable to shift relative alignment of the strip with respect to the cutter so that the cutter can partially or fully cut through the strip as desired. For example when applying a spacer strip around a rectangular glass sheet, starting at one corner and extending successively along each edge, at the second, third and fourth corners the spacer strip will be partially cut to facilitate its bending through a right angle at that corner, whereas when all four sides have been complete, the strip will be severed at the first corner.
In a preferred embodiment of the hand tool the cutter is in the form of a reciprocating punch or knife oriented substantially at right angles to the channel, and a displacement means is effective to displace the strip laterally in the channel so that the strip which is normally partially aligned with the cutter, but when the strip is to be severed, it is moved to become fully aligned with the cutter. It will be appreciated that the same effect can be achieved by arranging for the cutter rather than the strip to be displaceable laterally with respect to the channel.
The cutter can be in the form of a hollow tubular punch aligned to cut an arcuate notch out of the strip to facilitate bending thereof at a corner of the substrate, but capable of alignment to fully sever the strip when required. With this arrangement the strip is bent at the corner in a direction to close up or reduce the arcuate notch. In an alternative configuration the cutter is in the form of a knife which partially cuts through the strip to form a slit at a location where a corner is to be formed. It will be understood that in this configuration the strip is bent so that the sides of the slit lie approximately 90xc2x0 and face outwards at the corner of the substrate.
Where the strip within the channel is to be laterally displaced, this is readily effected by a simple pusher element carried in the side of the body and operable to displace the strip laterally when desired. While it is possible for the pusher element to be spring loaded and to engage a U-shaped cradle in the channel through which the strip is passed, displacing this cradle laterally when the strip is to be severed, in a simpler and much cheaper arrangement it is sufficient for the pusher element to be a plastic part loosely guided in a wall of the body adjacent the channel and having a pad surface that can engage the side of the strip material and push it laterally into an extension on the opposite side of the channel. No springs are necessary, and when the pusher element is released it will be restored to its non-actuated condition simply by the resilience of the strip material. The pusher element is furthermore preferably designed to clamp within the channel the severed end of the strip material leading from the supply, so that the strip material does not have to be re-threaded into the tool in subsequent application operations.
A method for use by an operator in applying an adhesive strip to a surface border area around the periphery of a rigid substrate having a flat major face, may involve the steps (a) locating the substrate in a generally upright position to present said major face towards the operator; (b) providing a hand tool which is adapted for manipulation by the operator for applying said adhesive strip to said substrate; (c) supplying a continuous length of adhesive strip material from a supply to said hand tool; (d) wherein the operator manipulates said hand tool to pass along said periphery to apply said strip of adhesive material to said border surface area of said major face around the entire periphery of the substrate.
The adhesive strip material is delivered from a reel behind the operator through an overhead guide to a discharge position above and in front of the substrate. Release liners on the strip are preferably peeled off as the strip exits from the guide.
Where the substrate is of rectangular outline with four corners, adhesive strip typically is applied starting at one corner and then continuously along the lengths of the four sides, the strip being notched or partially cut to facilitate its bending through 90xc2x0 at each of the second, third and fourth corners, and finally severed when it is returned to the first corner.
Conveniently where strip application is being done by a right handed operative, the starting point is typically the upper end of the left hand edge of the substrate. To facilitate the strip application operation and reduce operator fatigue the substrate is preferably mounted so that it can be moved vertically to a preferred working height. For example, use may be made of moveable suction cups which engage the substrate so that it can be adjusted vertically during application so that the instantaneous point of application of the strip is at all times conveniently located with respect to the operator.
The body and handle of the tool are preferably ergonomically shaped for comfort in use and to allow engagement of the tool by multiple and changing hand positions. The punch is preferably selectively operated by the fingers or thumb of the hand in which the tool is held, suitable actuators requiring pushing action from a finger or thumb onto a lever or button.
The components of the hand tool preferably are detachable, and the tool has a body to which the components can be attached alternatively for use in right handed or left handed mode. The tool includes a removable front face plate which at its lower end incorporates a slot at the top of which is a for guiding the strip into the tool channel, the face plate also including a large opening through which slugs cut from the strip by the punch are ejected.
The lower face of the tool is preferably provided as a removable wear plate, and the positioning member as a reversible pad that is releasably attached to the lower surface of the body, these parts being of plastic material which will minimize damage to the substrate.
The pressure wheel which rides on the strip within the tool channel is preferably height adjustable by means of a finger actuated rotatable nut carried by a threaded stem on which the pressure wheel is supported.
The invention will further be described, by way of example only, with reference to the embodiments illustrated in the accompanying drawings, wherein: